Satellite observations and in situ measurements for mapping bathymetry, sea bottom types and water quality in the gulf of Oristano (Sardinia, Italy)

This study aims to derive spatial and multi-temporal patterns of Posidonia oceanica meadow and to map bathymetry, by combining satellite data with in situ measurements. The study site is located in the northern part of the Gulf of Oristano, around the S. Marco cape. A physically based approach was used; it is based on radiative transfer equations connecting optical properties of the water column and of the sea bottom to the signal measured by the sensor. The inversion of all radiative transfer relationships allowed us to determine bathymetry and sea bottom types from remotely sensed data. In particular, the inversion is based on the codes 6SV for the atmosphere, and BOMBER for the water column. The database used consists of MIVIS, KOMPSAT-2, MERIS, RapidEye and WorldView2 images acquired in the period between 2001-2013. In situ measures were collected in August 2013; they were used to parameterize radiative transfer models and to validate RapidEye derived maps. Results show differences in bottom morphology and P. oceanica distribution between the two sides of S. Marco cape. A retrospective analysis allows to assess that the P. oceanica meadow is practically stable during the period 2001- 2013.